Process of recovering iron oxide and other products from spent iron sludgf



CHARLES V. BACON, OF 1-. l:

Be it known that I, Cmmms V; jBaooN, a citizen of the United States,resid at Mahwah, in the county of Bergen and tate 5 of New Jersey, haveinvented a new and useful Im rovement in Processes of Becovering ron.Oxide and Other Products from Spent Iron Sludge, of which the following1s a specification.

1o This invention relates to a process for utilizing the spent iron.sludge, commonly known as aniline reduction sludge, reductor slud e,etc., which is obtained as. a -by-prod-.- uct 0m the manufacture ofaniline, xylidine, toluidine, methaphenylenediami'ne and such otherproducts that yield a product which is usually magnetic and essentiallycom rises free or combined oxide of iron.

y investigations have led to the discovery that'theaforesaid s ent ironsludge, which heretofore has been either discarded as valueless or, whenthe ore market conditions permitted, converted by furnacing to'ironsinter, is admirably adapted for the produc-, tion of a high grade oxideof iron which is capable of serving as a bufiing or polishing material,paintpigment or jewelers rouge.

Furthermore, that in order to-accomplish the economical and homogeneousconver- 30 sion of suchsludge into hi h grade oxide of iron, it isessential to e ect such conversion under special conditions of concentration and temperatures all as hereinafter set "forth in detail.

In carrying out my intention, I preferably proceed as follows: Asufficient quantity of water is mixed in a suitable mixer with spentiron sludge, such as above defined, in order to convert the same into aasty mass containing about 30% water. %0 this mixture is then added,with constant stirring, an amount of sulfuric acid, about 70% strength,suificient to satisfy the iron oxide content of said sludge and onsubsequent heating convert the same into ferrous and ferric sulphatessubstantially according to the equation:

The concentration of the acid employed depends on the aqueous content ofthe mass of sludg'e'and should be sufiicientl dilute to insure that thewater content 0 the resultant mixture will be above the cunt hhtttounce;

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required to produce a pasty De endmg, on the moisture content of the sudge treated, the acid employed should be of such strength that themixture of water and acid contain at least 38% .water and willsubstantially correspond to acid of less than a strength of 50 B.otherwise the mixture will become substantially solid and the productionof the porous, spongy, sulphate-containing mass, hereinafter de scribed,cannot be obtained. The paste-like mixture of sludge and acid obtainedby the above treatment is heated, until the acid content has becomeconcentrated and the oxides converted into a orous, spongy massof'sulphates which is highly sulted for the production in a subsequent:furnacm operation of a homogenous pure 11'011 0x1 e. I a

The sulphates so obtained are then calcined for a sufiicient time at asuficiently high temperature todecompose the same into ferrlc oxide anda gaseous mixture of a strength sulphur dioxide and trioxide asrepresented substantially by the following equations:

tion, as described in my copending application NO. 348,775, which hasmatured into Patent Number 1,428,521, dated Feb. 14, 1922, wherein it isproposed to substantially prevent the formation of apasty mass such asis essential in the improved process herein described. Furthermore,' thedecompositions of said mixed sulphates as prepared by this processoccurs very readily, usually requiring but a few hours when; operatingon large charges. I r

The sulphuric acid, hereinbefore referred to, of 70% strengthcorresponds to 55 1%. and acid of 50 B. corresponds to acid of 62%strength.

No claim is made to the treatment of sulphuric acid and sludge mixturewhich contains less than 38% of water for as stated the novel andeficient results herein d escribed cannot he obtained if the mass comessubstantially solid almost immediately upon the addition of the acid tothe slu e. Y Pi eferably, however, the mixture of sulphuric acid andiron sludge contains not less than 50% of water.

Having thus described my invention, what I claim and desire to secure byU. S. Letters Patent is: v 1 l. The process which consists in subjectingiron sludge comprising essentially highly im ure iron oxide and while inafasty condition to the action ofaquantityo sulphuric acid suflicient toat least correspond to a substantially combining weight as compared withthe amount of iron oxids treated, heating the mass to a sufiicienttemperature and for a sufiicient time to concentrate the acid andconvert the mass into a porous spongy conditionv then elevating thetemperature and roasting the resultant mass to eifect the decompositionthereof into oxy-s ulphur acid quantity of an aqueous solution toconvert the same into a paste, subjecting said oxids while in such pastycondltionto the action of suflicient sul huric acid to substantiallysatisfy chemica y the iron oxide content thereof and then heating theresultant mass to a suflicient temperature and for a suflicient time toconcentrate the acid and convert the mass into a porous, spongycondition then elevating the temperature and continuing the heatinguntil the resultant sulhate-containing mass is decomposed into ironoxide and oxy-sulphur gases, then separately recovering said iron oxidein a substantially dry condition.

3. The process which consists in subjecting an aqueous mixture ofsulphuric acid and iron sludge, comprising essentially impure oxide ofiron mixed with not less than equal parts by weight of water, to aheating operation to concentrate the acid content thereof-and convertthe mixture into. a porous, spongy sulphate product and then heating theresultant mass to an elevated temperature for a suflicient time todecompose the sulphate contained in said mass into iron oxide andoxy-sulphur gases, then se arately recovering said iron oxide in a sustantially d condition. 7

Signed at ew York cit in the county of New York and State of ew Yorkthis3rd day of Oct, 1922.

GHAS. V. BACON.

